Relay control



Sept. 30, 1941. Q E LOMAX 2,257,265

RELAY CONTROL Filed April 22, 1958 I INVENTOR. Elarance ErnesTLumax W Mama/m ATTORNEYS larity in the appended claims.

Patented Sept. 30, 1941 UNITED STATES PATENT OFFICE RELAY CONTROL Clarence Ernest Lomax, Oak Park, 111., assignor to Associated Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware,

Application April 22, 1938, Serial No, 203,474

H lecting operation. More particularly, the wipers 2 Claims.

The present invention relates to improvements in apparatus for use in automatic telephone systems and, more particularly, to improved automatic switching apparatus for performing line selecting operations.

It is an object of the invention to provide improved apparatus for controlling the operating magnets embodied in a line selecting switch of the stepping type.

The invention is illustrated as being incorporated in a line selecting switch of the well-known Strowger step-by-step type, wherein vertical and rotary operating magnets are provided for stepping the wipers of the switch in their respective two directions of movement during a line selecting operation of the switch. In this type of switching mechanism each operating magnet is provided with an armature which is adapted to be moved toward the magnet pole faceupon energization of the magnet. As the armature approaches its associated pole face, the speed thereof increases for the reason that the air gap between the magnet pole face and the associated armature is decreased with a consequent increase in the force exerted on the armature. In order to reduce the shock incident to the meeting of the armature with its associated pole face, and in accordance with the present invention, there is provided in association with each operating magnet apparatus for reducing the speed of the asetiolated-operating armature as the armature approaches the pole face of the magnet upon energization of the magnet. More particularly, there is provided, in association with eachoperating magnet, electric circuit apparatus which is automatically operative to decrease the energization of the operatingmagnet following its energization and before the movement of its associated armature is completed.

The novel features believed to be character istic of the invention are set forth with particu- The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanying drawing in which the single figure illustrates a line selecting switch constructed and arranged in accordance with the present invention,

Referring now to the drawing, the mechanism there illustrated comprises the actuating apparatus for a step-by-step switch of the well-known Strowger type employing vertical and rotary movements of its wipers in eifecting a line seof the switch, not shown, are carried by a shaft 400 which is'adapted to be operated step by step in a vertical direction to position the wipers opposite a desired level of associated contacts by means of a ratchet and pawl mechanism which is arranged to be driven by a magnet, not shown, conventionally referred to as the vertical operating magnet. The mechanism for imparting rotary movement to the wiper carrying shaft I comprises a magnet 295, a ratchet wheel I formed integral with the shaft 300, and a pawl 462 carried by a pivotally mounted operating armature 493 oppositely disposed with respect to the pole faces of the core included in the magnet 295. The operating circuit for the magnet 29! includes a pair of armature springs 296 which are normally closed to short-circuit a resistor 295, and relay contacts indicated by the broken line for completing the circuit. The resistor 295' is arranged to be serially included in the operating circuit for the magnet 295 when the springs I are opened. These springs are under the control of a very light armature 404 which is normally spring biased by a light spring 485 to aposition for holding the springs 296 closed. The armature A is arranged opposite the heel piece end of the magnet 285 and, due to its light construction and light load, moves much faster than the operating armature 403 when the mag.- net 295 is energized.

With the springs 298 closed the initial energizing path for the magnet 295 is hy-passed around the resistor 295. When the magnet 285 is energized, however; the armature 404 is immediately attracted to open the springs 296 while the operating armature 403 is still moving toward the oppositely disposed pole faces of the magnet. When the springs 293 are opened the current through the winding of the magnet 285 is decreased since the resistor 295' is inserted in the circuit. Hence, the force exerted on the armature M3 is reduced and the speed of the armature is decreased before the armature completes its stroke. Thus, the shock incident to the completion of the stroke is materially reduced, thereby eliminating any possibility of the wipers being falsely operated more than one step and minimizing the vibrationthere'of. An identical arrangement may be provided in association with the vertical operating magnet of the switching mechanism for the same purpose.

By serially including the resistance element 295' in the operating circuit of the operating magnet 295 in the manner Just described, the

current traversing the circuit thereof is materially reduced immediately the armature 3 starts to operate. This reduction in the energizing current positively prevents the operating magnet from becoming overheated during operation thereof. Also, the current drawn from the current source is materially reduced during operation of the magnet. While in most instances the current consumption is of no great importance, in certain small telephone exchanges utilizing alternating current rectiflers the maximum power rating of the rectifier may at times tend to be exceeded during periods of heavy trafiic. By the arrangement illustrated wherein heavy current consumption occurs only during the initial period of each interval when the magnet is energized,

overloading of the current source is minimized. A further advantage of reducing the magnitude of operating currents flowing through the operating magnet, following the initial movement thereof and during each period of energization,

. of restoration of the magnet armature following deenergizatlon of the winding and positively eliminates sticking on the part of the armature.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In an automatic switch including a ratchet and pawl operating mechanism, an operating magnet having a pole face, a pawl operating armature adapted to be moved toward said pole face upon energization of said magnet, a circuit for energizing said magnet, said circuit including a normally short-circuited impedance element, means for completing said circuit, a second armature adapted to be attracted by said magnet upon energization, contacts controlled by said second armature and operative to remove the short circuit from said impedance element, said second armature being so constructed and arranged as to cause said short circuit to be removed from said impedance element before the movement of said first-named armature is completed, whereby the energization of said magnet is reduced during movement of said first-named armature.

2. In an automatic switch including a ratchet and pawl operating mechanism, an operating magnet having a pole face, a relatively heavy pawl operating armature adapted to be-moved toward said pole face upon energization of said magnet, a circuit for energizing said magnet, a

' relatively light armature adapted to be attracted by said magnet upon energization, and means controlled by said second-named armature for controlling said circuit to reduce the energization of said magnet during the preliminary movement of said'pawl operating armature, thereby to reduce the stroke-end speed of said pawl operating armature.

CLARENCE ERNEST LOMAX. 

